Was it Carb Ice?

[pelmet]

Carb heat is a good first item to check. Or.....check it on a regular basis while enroute.

C-GAKZ, a privately registered Cessna 172K aircraft was operating under visual flight rules from
Squamish Municipal Airport (Don Patrick Field) (CYSE), BC, to Pitt Meadows Airport (CYPK), BC,
with only the pilot on board. After descending to an altitude of approximately 1000 feet above
ground level (AGL) in the valley north of Indian Arm, the aircraft experienced a partial loss of
engine (Avco Lycoming O-320-E2D) power when the throttle was increased to climb. It was
reported that the degraded power output of the engine was insufficient to maintain altitude, and the
pilot began preparing for a precautionary landing. While the pilot was searching for a suitable
landing site, the aircraft engine lost all power, but subsequently resumed generating power without
pilot intervention. It was reported that the engine power output after the re-start was higher than
before the initial power loss, but still less than normal. The engine performance then degraded
further, and the engine stopped generating power a second time. The pilot successfully restarted
the engine, however the engine continued to produce insufficient power to maintain altitude. After a
brief period of operation, the engine quit a third and final time. At the time of the final power loss,
the pilot had maneuvered to the vicinity of a gravel bar on the Indian River. A low-level turn was
executed to align the aircraft with the landing site. Upon landing, the aircraft struck a log, which
caused significant damage to the left elevator and horizontal stabilizer. The aircraft came to a stop
on the gravel bar.

The pilot was uninjured and egressed the aircraft without issue. A hand-held personal locator
beacon (PLB) was activated at 1753 Pacific Daylight Time (PDT), and a Canadian Armed Forces
CH-149 Cormorant search and rescue helicopter retrieved the pilot at approximately 1958 PDT.
The aircraft was removed from the landing site several days later via helicopter.

Transportation Safety Board (TSB) investigators examined the aircraft after it had been recovered.
Investigators examined the aircraft engine and found no abnormalities. Fuel samples from the
engine gascolator were normal. Fuel samples taken from the aircraft wing tanks at the time of
recovery were examined and found to be consistent with the conditions to which the aircraft had
been exposed while awaiting recovery. With no abnormalities found with the aircraft engine, fuel
supply lines were reconnected with a fuel source and a successful engine start was performed. It
was determined that the condition that had caused the engine to quit during the occurrence was no
longer present at the time the aircraft examination.

[pdw]

Best Point, Indian Arm INORTH193 70.4F (21C) 67rh 6.09pm Aug 25. Serious icing at descent power.

[freakonature]

I once watched a c152 lose power on climb out. Student was panicking looking for help from the tower. He was about to go down in a very populated neighbourhood. Someone called on the radio and said pull the carb heat and away he climbed.

[lownslow]

Lycomings take a little more effort to ice up but I guess stranger things have happened.

[Dry Guy]

I'd be testing my fuel hard if I was in Squamish.

[pdw]

It does look obvious it was carb ice conditions, but most of the time only the pilot involved can confirm if it “was”. A number of carb ice incidents continue even as fewer planes have carburators.

Highlighting every carb heat/ice incident is one way to keep new & old pilots alike informed how many incidents are actually still occurring with this older style aircraft carburator system icing.

So the point that could be made here is that since new and older pilots now often do alternate between AC with or without a carburator, it means they potentially wouldn’t be focused as routinely on a carb issue 24/7 (maybe aren’t hearing about it as much either) as in days gone by. No one wants to admit it? Could this mean more icing accidents than before … where everyone was most attentive to carburator ice at all times, no exceptions?

[pdw]

Old thread. Bumped it only in noticing that this question should be easier answered in most cases imo. It looks like there are a lot of carbheat misses still, just looking at some of the accidents (against the carb ice chart bullseye temps) wakes one up. Back when almost every aircraft needed the careful monitoring of carburator substrates there was a real support structure to encourage thorough monitoring of the carbheat, and it was talked about a lot more (for prevention) since every flight prepared for it and monitored constantly.

[pelmet]

I see that this particular C172 had a Lycoming O-320 engine which is considered to be less susceptible to carb ice. But apparently it does happen sometimes. Possibly on a C172 at a local flying club that I am a member of that had one crash recently. On the other hand, as a member of another flying club, I overheard an instructor telling another pilot that in 4000 hours of 172 flying(lycoming engine version), he had never seen carb ice on that type.

Perhaps a danger is the rarity of it happening so one is not taking proper precautions. Just check the carb heat on a regular basis. And remember that if you have been flying Lycoming 172's and go to an earlier Continental model, the risk level may be much higher. Meanwhile, I did a flight a couple of days ago in a Lycoming model and used the carb heat not only on the downwind for each circuit but continuously when flying in the local area through some light rain. I believe that precipitation areas increase the likelihood of carb ice. I base this on reading a pilot report on a different aircraft type and their carb ice experience in a rainshower versus no ice outside the shower.

Below is an interesting comment that I found on another site.....

"........the original Cessna 172's had Continental O-300 engines in them, which due to their design, were susceptible to carb ice especially at low power settings. It was in the POH and well-advised to use carb heat at these settings. The O-300 version of the manuals used to suggest you leave the carb heat on until right when you start your takeoff roll. In fact, the fact that ground ops may cause carb icing *IS* specifically mention in these older manuals.

Later, the planes got re-engined with Lycoming O-320 engines (and later with injected versions of this which don't have carb ice problems at all lacking a carb). The Lycomings due to their construction are less susceptible to carb ice (the carb is warmed by the oil sump).

The later (O-320) POHs do indeed say to use carb heat on approach. It's Item #4 on the "BEFORE LANDING" checklist. This comes for exactly the reason you were given. Colder engines are more prone to carb ice (see later in this post). It tells you to turn carb heat off on the ground because the carb heat bypasses the air filter and this results in the potential for dust from the ground being sucked into the engine.

My Navion had a pressure carb. This is reputed to relatively immune to carb ice. We flew it back from doing work at a nearby airport and it was a relatively mild day. Since we weren't going far (and 260 HP will move the Navion along pretty fast), my wife was flying at a much reduced power setting. About the time we hit the pattern at our destination, the engine falters. I tell her to head right for the runway and she does so and lands fine. It occurred to me after we rolled on to the taxiway. I pull the carb heat control and tell her to give it a little throttle . Yep, carb ice. The only time other than in the O-300 Cessna 170 I've encountered it."

[CpnCrunch]

Yes, carb ice is rare on carburreted Lycoming 172s, but it does happen occasionally. Certainly not as often as on continentals (especially the C150), where it's a regular occurrence. I think it's only happened to me a few times, always flying near the ocean.

So yes, if it only happens very occasionally, the pilot may not realise what it is.

Most of my carb icing has been at full throttle on climbout on sunny days, when you may (incorrectly) believe that there isn't any chance of carb icing.

[CensoredLF]

Indeed the dreaded C150 (O200) trains you for carb ice.
- new plane to us, BC Lower Mainland, August high humidity, I was warned by the AME, and a 150 had gone down on takeoff the week before. Sure enough the engine sputtered on the first take off roll.

- regularly in Alberta when ground temp is 5 to -5 the engine starts coughing when cruising at top speed
An excellent way to look the calm professional hero type when it occurs with an attractive passenger

But it is extremely scary the first time, even if you recognize the symptoms. Will the carb heat be effective?

YMMV
CLF

[Deadcat]

Conducting a checkride in a PA140 the other day on the forced approach exercise I noticed the pilot did not apply carb heat. I asked him why and he replied “not in the POH”. Conscientious guy otherwise, so I guess there’s a good slice of pilot population thinking that way.

[CpnCrunch]

Conducting a checkride in a PA140 the other day on the forced approach exercise I noticed the pilot did not apply carb heat. I asked him why and he replied “not in the POH”. Conscientious guy otherwise, so I guess there’s a good slice of pilot population thinking that way.

The green in the PA28 RPM gauge goes down to 500rpm, and the POH says "carburetor heat should not be applied unless there is an indication of carburetor icing, since the use of carburetor heat causes a reduction in power which may be critical in the case of a go-around". You can just put carb heat on for a few seconds during the prelanding checks. The reason is because the carb in the PA28 gets some heat from the engine, so is less susceptible to icing.

Still, carb icing is still possible in the PA28:

https://asn.flightsafety.org/wikibase/291580

[pdw]

not in the POH

Thought it was also a pilot’s ‘need to know’ about any/every meteorology factor(s) creating ice formation possibility inside intake/carberator and how/when to utilize supplied carb heat devices made available. How is a POH supposed to contain advice on ALL conceivable combinations possible for that ice’s formation.

[digits_]

not in the POH

Thought it was also a pilot’s ‘need to know’ about any/every meteorology factor(s) creating ice formation possibility inside intake/carberator and how/when to utilize supplied carb heat devices made available. How is a POH supposed to contain advice on ALL conceivable combinations possible for that ice’s formation.

There's a difference between a POH telling you to use carb heat on every descent vs one telling you to use it when carb ice might be expected for example.

[‘Bob’]

I encounter this paradox early in my instructing career. Cessna's need carb heat always, Pipers don't. I didn't believe it because the engine in a 172 and a Cherokee are virtually identical.

The reason is that Cessnas used to be powered by Continental engines which are ice magnets. When it swapped to Lycoming for the 172 and eventually for the 152, it was simply safer to leave the relevant passages in the POHs for commonality and liability purposes.

From experience, Lycomings are less prone to ice but definitely can pick up a lot of ice under the right conditions in both Pipers and Cessnas. When in doubt, just use it. If you are at a low power setting the loss in power doesn't really matter anyways.